File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

APP file extension

Mac OS X Application

Executable Files

AVI file extension

Audio Video Interleave File

Video Files

CPL file extension

Windows Control Panel Item

System Files

CS file extension

Visual C# Source Code File

Developer Files

DAT file extension

Data File

Data Files

DXF file extension

Drawing Exchange Format File

CAD Files

FLV file extension

Flash Video File

Video Files

GADGET file extension

Windows Gadget

Executable Files

NES file extension

Nintendo (NES) ROM File

Game Files

PIF file extension

Program Information File

Executable Files

PPTX file extension

PowerPoint Open XML Presentation

Data Files

PSD file extension

Adobe Photoshop Document

Raster Image Files

RSS file extension

Rich Site Summary

Web Files

RTF file extension

Rich Text Format File

Text Files

TAR file extension

Consolidated Unix File Archive

Data Files